The Fluval Tronic Submersible Electronic Heater offers a technologically advanced operation system that delivers accurate, responsive, safe and reliable heating for fresh and saltwater aquariums. The patented thermal sensor continuously monitors the aquarium's water temperature to maintain precise temperature control. The unit heats continuously until the selected temperature has been achieved, providing quick and accurate temperature control. There are no mechanical components to wear. The numeric temperature dial makes it easy to select desired temperature. The safety shut-off feature allows the heater to switch off if it is accidentally removed from the water, or in situations when low water levels occur. Ideal for aquariums up to 45 US gallons (150L).